This invention relates to automatic clutches adapted for use with a motive power source, and more particularly relates to a novel and improved automatic centrifugal clutch with a manual override control mechanism for motorcycles.
Motorcycles employ internal combustion engines either of the two-stroke or four-stroke variety, the fuel being ignited by an electric starter to cause the pistons to advance through their respective cylinders and to turn the engine crankshaft via a connecting rod which joins the piston and crankshaft together. The crankshaft converts the up and down movement of the piston to a circular motion which operates through a gear or chain reduction to power a pinion into the primary drive gear on a clutch housing. This permits the rider to disconnect the engine from the transmission in order to shift from one gear to another. The clutch itself is operated by a hand lever so as to allow power to be fed gradually from the engine to the gearing or to be disconnected for gear changing. Also, in the standard motorcycle, a gear shift is controlled by a foot lever to engage or disengage the transmission depending upon whether one wants to idle or cause the gears to impart rotation of the crankshaft into the rear wheel. In most street bikes an electric starter is employed, and in emergency situations it is possible to bumpstart by running alongside the motorcycle with the manual clutch pulled in and transmission in the lowest gear that won""t lock up the rear wheel, then hop on and pop the clutch as one hits the seat.
In off-road motorcycles, referred to as xe2x80x9ctrailxe2x80x9d or xe2x80x9cdirtxe2x80x9d bikes customarily there is no electric starter to start the engine; instead, a kickstart foot lever operates through a primary gear on the clutch housing to rotate the crankshaft and start the engine very much like the hand crank employed in early model automobiles. When used in conjunction with an automatic clutch the kickstart lever imparts rotation directly to the outer basket or housing portion of the clutch via idler gears in a crankshaft set to the engine. Previously, at least in the automatic clutch versions, it was not possible to bumpstart by popping or manually engaging the clutch after getting up to speed.
It has been proposed in the past to utilize a central push rod in the clutch housing which when activated will release the friction plates in the clutch against spring pressure, representative patents being U.S. Pat. Nos. 4,518,070, 3,842,954 and 3,215,234. Nevertheless, no practical way has been devised previously to mechanically engage the automatic clutch for purposes of bumpstarting it in emergency situations. Therefore, it is desirable to provide a simple but highly effective means of manually engaging an automatic clutch through the utilization of the existing clutch mechanism and specifically to employ a push rod in the reverse manner to cause the clutch plates to engage by forcing a series of rolling members out along an inclined surface or ramp to overcome the spring pressure normally retaining the clutch plates out of engagement. In this way, it is possible to bumpstart the engine by engaging the transmission gears, rolling the motorcycle along the ground to reverse the transmission from the rear wheel into the transmission shaft centrally of the clutch housing, followed by activating the push rod to engage the clutch and rotate the crankshaft through the primary driven gear in the clutch housing. Moreover, the automatic clutch will be normally disengaged at lower rpms or when the engine is idling and therefore not require manual disengagement each time that the motorcycle is slowed down or stopped.
In bumpstarting, it is important to understand that the initial turning or rotational movement required for rotation of the transmission shaft must be imparted by rotation of the rear wheel back through the gear reduction drive into the transmission shaft and which can be done simply by rolling or advancing the motorcycle along the ground. Secondly, it is necessary to shift the gearing from neutral into one of the gear positions, such as, second gear whereupon activation of the push rod to engage the clutch will impart rotation to the crankshaft and start the engine without the kickstarter.
Accordingly, there is a need for an emergency starting mechanism for automatic clutch type motorcycles and other applications as well but particularly for use in off-road vehicles which can employ the existing drive train of the motorcycle and impart the necessary turning force to start the engine without the assistance of a kickstarter or electric starter. Moreover in standard motorcycles there is a need for a clutch lockout so as to make automatic clutches feasible for use with electric starters.
It is therefore an object of the present invention to provide for a novel and improved method and means for bumpstarting an internal combustion engine which is highly dependable and effective in use while requiring a minimum of manual exertion or effort.
It is another object of the invention to provide for a push rod in combination with a centrifugal clutch which is capable of selectively engaging the clutch plates of an automatic clutch without imparting any centrifugal force to the clutch-engaging members.
It is a further object of the present invention to provide for a novel and improved clutch-engaging mechanism which requires minimal movement of an activating member to effect engagement of the clutch plates of an automatic clutch and wherein the starting mechanism is conformable for use with different types of existing automatic clutch mechanisms.
It is a still further object of the present invention to provide a manual control for an automatic motorcycle clutch, either in the form of a push rod or pull rod, which enables the clutch to remain in a normally released position when at low speeds or idling and can effect manual clutch for bumpstarting.
In accordance with the present invention, there has been devised a novel and improved manual control mechanism for an automatic clutch interposed between an engine crankshaft and a transmission shaft wherein the clutch is provided with an inner hub coupled to the transmission shaft and an outer cover coupled to the crankshaft with clutch members alternately extending from and fixed for rotation with said hub and said cover portion and being axially displaceable into and away from frictional engagement with one another, a clutch-engaging member at one end of the clutch members including spring means biasing said pressure plate away from the clutch members, and centrifugal force-responsive means movable radially and outwardly along said pressure plate to overcome the spring means and force the pressure plate axially against an endmost of the clutch members whereby to impart rotation between the basket and the hub, the mechanism comprising control member actuating means between one end of the control member and clutch-engaging member being movable in response to axial movement of the control member to displace the clutch-engaging member in an axial direction independently of the spring means, and manual control means for selectively advancing and retracting the control member in an axial direction whereby to manually control engagement and release of the clutch members independently of the speed of rotation of the clutch housing.
In a preferred form of invention, the manual control member is a push rod or pull rod for selectively engaging the clutch members by forcing the clutch-engaging member to overcome spring pressure and compress the clutch plates into firm frictional engagement so that the transmission shaft rotation is imparted to the crankshaft through the clutch housing. The clutch-engaging member may either take the form of a pressure plate within the clutch housing or the clutch housing itself in manually engaging the clutch to bumpstart the cycle.
In other modified forms of invention the push rod or control rod is employed in an automatic clutch to mechanically lock the clutch in a neutral position so that the clutch cannot be engaged without manually releasing the control rod; otherwise, when the control rod is depressed it will prevent the pressure plate from engaging the clutch plates and the clutch remains disengaged even when the engine reaches a speed that would normally cause the clutch to engage. If desired, a dual control mechanism may be utilized to releasably lock the clutch in a neutral position or to manually engage the clutch for bumpstarting the cycle.
There has been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.